Method for making cellular material



Jan. 23, 1968 s. RICHARDSON E 3, ,7 0

METHOD FOR MAKING CELLULAR MATERIAL Original Filed Feb. 4, 1963 5 zaw EII] CI] III] TIHIIIIZ] 650 665 B /Vim #42002: A. F 868 MZfI/VK. 06/1/65)zigwu United States Patent 3,364,729 METHOD FGR MAKING CELLULAR MATERIALGeorge Richardson, Lynn, Mass, Theodore Norton Ferren, Acton. Maine, andWarren Clifton Denley, Saugus, Mass, assignors to General ElectricCompany, a corporation of New York Griginal application Feb. 4, 1963,Ser. No. 255,866, now Patent No. 3,226,905, dated Jan. 4, 1966. Dividedand this application Mar. 22, 1965, Ser. No. 459,964

3 Claims. (Cl. 72-341) ABSTRACT (BE THE DISCLGSURE A cellular structureis made by first perforating appropriately a sheet material to producean interconnected pattern of cell units in the sheet. By bendingportions of each cell unit of the sheet in a repeating pattern, thereare formed a plurality of cells projecting generally away from the planeof the sheet material.

This is a divisional application of application Ser. No. 255,866 filedFeb. 4, 1963, issued Jan. 4, 1966 as a US. Patent 3,226,905 and assignedto the assignee of the present invention.

This invention relates to a cellular material, particularly 0f thehoneycomb-type including an integral base and capable of continuousmanufacture.

Over the years, the developement of the manufacture of honeycomb-typecellular structures has produced a large variety of types of structuresand methods of manufacture. These can be seen in the large numbers ofavailable patents and other publications. While most of the knownmethods and structures involve the joining of separate, independentelements into a honeycomb structure, continuous methods of making suchcellular materials have been reported in patents such as US. 2,933,122and US. 3,017,97l-Christman.

Honeycomb-like cellular materials are characterized by light weight andgenerally high strength in a direction substantially normal to theOpenings in the cells. However, in order to use the cellular material asa structural member or as a seal such as in flight propulsion equipment,it is necessary to attach the cellular material to another structural orbacking member or to sandwich the cellular material between a pluralityof substantially solid structural members. Because prior cellularhoneycomb-like materials do not include integral base members, it wasnecessary to use such attaching methods as pressure Welding and brazingin an attempt to achieve substantial attachment of the thin wallstructure to a backing member. Brazing is used most frequently. However,brazing methods require additional materials which add to the weight ofthe structure. Furthermore, the brazing of some honeycomb-type materialsfor seal purposes to the inside diameters of backing members hasresulted in many bonding failures. Because of the different coefficientof expansion, the honeycomb material could not be held in contact withthe backing member during brazing.

It is an object of the present invention to provide a method for makinga cellular material including base members integral with the material toafford case of attachment such as by spot welding of the cellularmaterial to a backing member.

Another object is to provide a method for making a cellular material,with an integral base, in a continuous strip by an improved andrelatively inexpensive method of production,

Still another object is to provide a method for making a continuoushoneycomb-like structure including an inte- 3,3543% Patented Jan. 23,1958 gral base, manufactured from a continuous strip of sheet material.

These and other objects and advantages will be more readily recognizedfrom the following detailed description and the drawing in which:

FIGS. 1-3 are fragmentary plan views of cell units which form the basisof the structure of this invention;

FIG. 4 is an isometric fragmentary view of a portion of the structure ofthe present invention in an intermediate step in its manufacture;

FlG. 5 is a composite plan view of progressive steps in the method ofthe present invention;

FIG. 6 is a cross-sectional view through AA of FIG. 5;

FIG. 7 is a fragmentary plan view base side up of the structure of thepresent invention; and

FIG. 8 is an isometric fragmentary view of the structure of the presentinvention attached to a backing sheet for use together as a sealingmember.

Briefly, the cellular structure of the present invention is made up ofrows of cells including integral base members alternating with rows ofopen cells not including base members. The base members connect thelateral Walls of those cells which include such base members, and tabmeans connect the tops of the lateral walls of each of the consecutiverows of cells having base members. The base members and the tab meansalternatively interconnect consecutive rows of the cells including basemembers into a continuous structure. When doing so, the external wallsof the cells including base members create or define the peripherallimit of open cells, not including base members.

The method of the present invention in one form comprises perforatin aflat sheet material to produce a plurality of interconnected sheet cellunits, Each of the sheet cell units comprises first and second celllateral wall members, a cell base member and first and second tabmembers. The cell base members extend between the first and second wallmembers and the first and second tab members extend from the first andsecond wall members respectively in opposite directions from the basemember. The method continues by bending the lateral wall members of eachof the plurality of cell units into a wall shape desired for a cell ofthe cellular material. The lateral wall members formed in this way foreach of the cell units are then bent one toward the other along a linefrom which the base member extends from each Wall member to contactaligned outer portions of the lateral wall members while at the sametime bending the interconnected tab members of adjacent cell units onetoward the other along their lines of connection. Thus a plurality ofcells including base members are formed from the plurality of cell unitsand a plurality of open cells are defined by the lateral Walls ofadjacent rows of cells including base members.

The cellular structure of the present invention, shown in the isometricview of FIG. 8 attached to a backing member, reduced to its simplestform at the start of its manufacture consists of a sheet cell unit shownin various forms in FIGS. 13, as elements it 12 and 3.4. Each sheet cellunit includes a pair of lateral wall members 16, a base member 18, 18aand 18b and a pair of tab means 20, 29a and Zilb in FIGS. 1, 2 and 3respectively. Generally, the shape of lateral wall members 16 ismaintained substantially rectangular because the wall members determinethe thickness, or depth, of the final cellular material. It is generallydesirable to maintain the thickness uniform across the material.However, it is possible without deviating from the scope of thisinvention to modify the shape of the cell lateral wall members ifnonuniformity in thickness of the cellular structure can be tolerated oris desirable. However, the shape of the base member and the tab meanscan be varied from the rectangular shape 13 in FIG. 1 to the curvedshape of 18a in FIG. 2 or the diamond shape of FIG. 3 depending (1) uponthe degree to which it is desired to fill the base of the cellularmaterial in the final product and (2) upon the shape in which thelateral wall members of the cell units are bent in specifying the shapeof the cells of the cellular material.

Referring to FIG. 1, it is noted that base member 18 extends betweenlateral wall members l6 and that the tab means 2%) extends from thelateral wall members on sides of the wall members opposite from that atwhich the base means is extended. A plurality of continuous sheet cellunits can be formed by perforating a flat sheet of material, a fragmentof which is shown generally at 22 in FIG. 1, to produce a plurality ofinterconnected sheet cell units gg, h-h, i-i, jj, k-Jc, ll, mm and n-iz,shown in phantom, which generally surround the example sheet cell unitit? in FIG. 1.

It is noted that sheet cell units hh and m-m are aligned with sheet cellunit it} along the Y direction which in this specification forillustration is referred to as the length or column, and sheet cellunits 'j and kk are aligned in the X direction which is referred toherein for illustration as the width or row. In the examples of FIGS. 1,2 and 3, the base members and the tab members extend centrally from thefirst and second wall members. This symmetrical arrangement has beenfound to be the best from the standpoint of ease of manufacture and costof perforating or bending dies because the dies can be used in arepititious process to perforate or bend a piece of fiat sheet materialfed continuously beneath them.

Thus the first stem in producing the cellular material of the presentinvention is to perforate or punch from a fiat sheet of material aplurality of particularly located openings. The resulting structureforms a plurality of interconnected sheet cell units of the type shownin FIGS. 1-3.

The second step in the manufacturing method is to bend or shape thelateral wall members 16, FIGS. 1-3, to a wall shape desired for a cellof the cellular material. This can be done immediately after perforatinor punching flat sheet material by pressing the lateral wall membersbetween two shaped dies. The classical hexagonal shape can be producedin the final product by bending the outer one-third portions of each ofthe lateral wall members one toward the other to form a channel alongthe length of the sheet material with the base member and tab meanslying along the bottom of the channel. It has been found, however, thata preferred method of bending the lateral wall members is by corrugatingthe perforated sheets so that the corrugation furrows and ridges extendalong the length of the sheet with the bottom of the furrow lying alongthe line of the base member and tab means. A portion of sheet material22 of FIG. 1, after such corrugation is shown in FlG. 4. The perforatedand corrugated fiat sheet material of FIG. 4, when viewed incross-section in the X direction would have the appearance of a sinewave with the points of inflection of the furrows and ridges alternatingsubstantially along the juncture between the lateral wall members ofadjacent cell units, such as cell units 'j, 10 and respectively, andalong the co-linear base and tab members 18 and 26 of FIG. 1. Cell unitsformed by corrugating the sheet material after perforating and prior tofurther forming will ultimately result in a cell structure shown inFIGS. 7 and 8 wherein the characteristic sharp hexagonal honeycomb shapeis replaced by a curved shape.

After the lateral wall members of each of the plurality of cell unitshave been bent in the desired shape, the lateral wall members of eachcell unit are bent one toward the other along the line from which basemember 18 extends from each of the wall members until the aligned outerportion of the lateral wall members of aligned cell units contact oneanother. For example, in FIG. 1, the cell lateral wall member 16 nearerto cell unit h-h is bent upward from the plane of the drawing along aline from which base member 18 extends from that cell lateral wallmember while at the same time the cell lateral wall member 16 nearer tocell unit mm is bent up from the plane of the drawing, and thus towardthe other lateral wall member of cell unit it), along a line from whichbase member 1'8 extends from that cell lateral wall member. At the sametime, during manufacture of a continuous structure, the adjacent cellunits j and kk along with the associated tab means of cell units gg, hh,ii, 1-1, m m and 11-22, etc., will be similarly bent. The cell lateralwall members 16 are thus bent one toward the other unitl the line ofjuncture between the lateral wall members of cell units 10 and j and thejuncture between the lateral wall members of cell units k-k and 10 arein contact. At the same time the interconnected tab members of adjacentcell units aligned along the length of the sheet material are bent onetoward the other along their lines of connection. In this way thecompleted cellular structure shown in FIGS. 7 and 8 and at the top ofFIGS. 5 and 6 are formed.

When working with sheet metal which has a tendency to spring back slihtly from bending operations, it might be necessary, additionally, topinch together the bent tab members 20 in order to maintain the lateralwalls of adjacent rows of cells in substantial contact or closeproximity. In this way two types of cells are formed in alternating rowsin the structure of the present invention. These two types of cells areindicated in FIGS. 5 and 7 as D and E. The D type cell includes a basemember 13 whereas the E type cell does not include a base member. The Etype cell is referred to herein as an open cell. The final structure,made from a continuous sheet which has been punched and bent, is heldinto a continuous interconnecting structure alternatively by the basemembers 1% and the tab means 20. The lateral walls of consecutive rowsof D type cells, when contacting one another, create the type E or opencells.

As shown in FIGS. 6 and 8, tab means 20 can extend above the lateralwall of the structure. This provides in the structure of the presentinvention the spring-like ability to expand with an expanding backupmember Such as 23 in FIG. 8 to which the base members of the cellularstructure can be welded. In this way a rubbing type seal usedextensively in gas turbine engines, can be made.

FIGS. 5 and 6 are composite views of one method of manufacturing thecellular material of the present invention described above. Starting atthe bottom of H6. 5, a plurality of substantially rectangular openingsare perforated in sheet metal 24 to produce the sheet cell units shownin phantom in FIG, 5 and bearing like numbers to those cell unitsdiscussed before. That portion of FIG. 5 bracketed and identified as Crepresents the appearance of the cell units and sheet metal structureafter corrugation as described above. The top of FIGS. 5 and 6 show thecompleted structure. FIG. 5 is a plan view from the top with the tabsside up and the bases farthest from the viewer. FIG. 7 is a plan view ofthe finished structure with the base side up and the tabs farthest fromthe viewer.

Although the structure and method of manufacture of the presentinvention has been described in connection with specific embodiments, itwill be recognized by those skilled in the art the variations andmodifications, such as the shapes of the various elements, withoutdeviating from the basic invention of a cellular honeycomb-typestructure including an integral base economically and continuouslymanufactured from sheet material.

What is claimed is:

1. A method of making a cellular structure from sheet material,comprising the steps of:

perforating the sheet material to produce a plurality of interconnectedsheet cell units, each sheet cell unit comprising:

(a) first and second cell lateral wall members,

(b) a cell base member extending between the first and second wallmembers, and (c) first and second tab members extending from the firstand second wall member respectively in opposite directions from the basemember; bending the lateral wall members of each of the plurality ofcell units to a wall shape desired for a cell of the cellular structure;bending the lateral wall members of each cell unit one toward the otheralong a line from which the base member extends from each wall member tocontact aligned outer portions of the lateral wall members; while at thesame time, bending the interconnected tab members or" adjacent cellunits one toward the other along their lines of connection, whereby aplurality of cells including base members are formed from the pluralityof cell units and a plurality of open cells are created by the lateralwalls of adjacent rows of cells including base members. 2. A method ofmaking cellular structure from a sheet material, comprising the stepsof:

perforating the sheet material to produce a plurality of symmetricalinterconnected sheet cell units, each sheet cell unit comprising:

(a) first and second cell lateral wall members, (b) a cell base memberextending centrally between the first and second wall members, and (c)first and second tab members extending centrally from the first andsecond Wall member respectively in opposite directions from the basemember; bending the lateral wall members of each of the plurality ofsymmetrical cell units to a wall shape desired for a cell of thecellular material; bending the lateral wall members of each cell unitone toward the other along a line from which the base member extendsfrom each wall member to contact aligned outer portions of the lateralwall members; while at the same time, bending the interconnected tabmembers of adjacent cell units one toward the other along their lines ofconection; and then pinching together the bent tab members, whereby aplurality of cells including base members are formed from the pluralityof cell units and a plurality of open cells are created by the lateralwalls of adjacent rows of cells including base members. 5. A method ofmaking a continuous cellular structure from a continuous sheet material,comprising the step of: perforatin the sheet material to produce aplurality of symmetrically interconnected sheet cell units, each sheetcell unit comprising:

(a) first and second cell lateral wall members, (b) a cell base memberextending centrally between the first and second wall members, and (c)first and second tab members extending centrally from the first andsecond wall members respectively in opposite direction from andco-linearly with the base member but on opposite sides of theirrespective wall members; corrugating the perforated sheet so that thecorrugation furrows and ridges extend alternatively along the length ofthe sheet with points of inflection of the furrows and of the ridgesalternating along the width of the sheet substantially at the juncturebetween the lateral wall members of adjacent cell units and at theco-linear base and tab members; bending the lateral wall members of eachcell unit one toward the other along a line from which the base memberextends from each wall member to contact aligned outer portions of thelateral wall members; while at the same time, bending the interconnectedtab members of adjacent cell units one toward the other along theirlines of connection, whereby a plurality of cells including base membersare formed from the plurality of cell units and a plurality of opencells are created by the lateral Walls of adjacent rows of cellsincluding base members.

References Cited UNITED STATES PATENTS 2,933,122 4/1960 Christman 52666X 3,108,367 10/1963 Christman 29455 X 3,162,942 12/ 1964 Christman 29455 FOREIGN PATENTS 189,297 11/ 1922 Great Britain.

CHARLIE T. MOON, Primary Examiner.

